An independent Palestinian television station is facing a potentially crippling court case next week amid growing evidence of a clampdown by the Palestinian Authority on freedom of expression and journalists critical of its activities.

Wattan TV is being sued for $1m (£600,000) over an investigation into alleged corruption at a Palestinian university. It claimed that the son of a senior PA official was offered a place at the university despite having failed to meet academic requirements. The station, which says it has evidence to support its allegations, fears that some of its executives could face prison sentences and that freedom of speech in the Palestinian territories will be curtailed.

It follows the resignation last week of the Palestinian communications minister in protest at the PA's blocking of at least eight websites that criticised President Mahmoud Abbas.

Mashour Abu Daqa said the closure of the sites was "bad for the image of the [PA] in the modern world" and that restricting access to information was a form of corruption. "Blocking websites is against the public interest. I oppose it without exception," he said.

Most of the targeted websites were associated with Mohammed Dahlan, an arch-opponent of Abbas within the ruling Fatah faction.

The attorney-general, Ahmad al-Mughni, issued a statement on Sunday confirming that some sites had been blocked following complaints from individuals and others were censored for security reasons.

The US voiced its concern over the move. "We are concerned about any uses of technology that would restrict access to information," said state department spokeswoman Victoria Nuland. "We've had these concerns [about freedom of expression] in other parts of the world, and we wouldn't want to see the PA going in the direction that some of those regimes have gone in."

Veteran Palestinian politician Hanan Ashrawi condemned the blocking of the websites as "measures that … undermine our efforts to create a Palestinian democratic, pluralistic and tolerant society based on the rule of law. It is imperative that we safeguard the freedom of expression, access to information and all other fundamental human rights of the Palestinian people."

Critics fear that some senior figures in the PA are urging greater censorship and interference in online activities that are perceived as unsupportive. According to human rights groups, at least seven journalists and bloggers have been detained and interrogated by PA security forces in the past few weeks over opinions expressed on websites or Facebook.

One of those arrested, amateur cartoonist Hasan Wa'el Abbadi, 23, has been charged with "creating disunity among the people", according to al-Haq, a human rights organisation. He was released on $4,000 bail pending a court hearing. Former university lecturer Ismat Abdel Khalik was detained for "insulting" Abbas after describing him on her Facebook page as a traitor and fascist.

"We have great concern regarding this campaign against bloggers and journalists," said Sharwan Jabarin, director of al-Haq. "Maybe the attorney-general is trying to send a message. Maybe they don't want people to talk about corruption."

According to Muamar Orabi, the general director of Wattan TV, media repression is growing. "We are facing the worst time for independent journalists in the PA. Journalists are being arrested just for raising their voices and speaking freely. This is very, very dangerous. We need independent, credible voices."

Wattan's mission statement says it "advocates democracy, peace, justice and political pluralism" and "promotes human rights and a transparent government accountable to the Palestinian people". The non-profit station was founded by three Palestinian civil society organisations in 1996, and the US and EU are among its donors.

Between 1996 and 2002, Wattan was closed down five times by the PA. But it has also been targeted by the Israeli military, which raided the station in 2002 and destroyed its equipment. On 29 February this year, Israeli soldiers again forcibly entered its premises in the middle of the night, ransacked offices and confiscated valuable equipment and documents, according to Orabi.

Israeli officials claimed Wattan's transmitters were interfering with communications at Israel's Ben Gurion airport. Wattan says its frequency is registered legally in the PA and the International Broadcasting Union in Switzerland.

Reporter Shireen Far said Wattan's staff believed there were political motives. "Israel does not want people to know what its occupation is doing, they want the Palestinian people to be blind," she said.

The combined impact of the Israeli raid and the Palestinian lawsuit was difficult for the station's journalists. "The job of journalists is to tell the truth despite the difficult conditions," she said.

Ghassan Khatib, director of the Palestinian government media centre, said the closures and arrests were the responsibility of the attorney-general. "The government believes in freedom of opinion and expression," he said.